I understand what you're getting at with the tray, it was misused by "me too!" programs and all sorts of things like Real Player (damn, I'll run you when I want it!).
But it was very useful to interact with e.g. virtual CD-ROM drive software. That's better than having "background" programs sitting in the task bar proper.
To this day most linux desktop environments copied the feature and I've got wireless networks, sound volume, music player there, OS updater. I can play/pause music etc., change music volume by hovering on the icon and wheeling the scroll wheel. I know how to run fluxbox and hit the terminal to run alsamixer but I'll keep running the gtk2 Windows 95 clone thanks.